How to prevent SPAM from your own domain

Sometimes on a professionnal mailbox, you can receive SPAM from your own domain and maybe even from your own email address. If you are in this case, the first thing to do is to analyze the email header in order to see from which SMTP server the email is coming : Either the SMTP server is really your internal SMTP, which means that one of your LAN machine is probably infected, or your SMTP server is an open relay Either you will see that the email is routed by an external SMTP server, spoofing your own address, before being delivered to you. That's a good thing, in this case, you will be able to stop it. Explanations Anyone with sufficient knowledge can send an email with any address in the "From" field. It's like that since the beginning of the emails ...